In recent years, various light-emitting devices using light-emitting elements, such as light-emitting diodes (LEDs), have become commercially practical. In such a light-emitting device, light-emitting elements are attached to an inner side of a concave portion that is provided for a container made of a resin, for example, and this inner side is used as a reflection surface of light emitted from the light-emitting elements. Here, at the bottom surface of the concave portion, a metal lead portion for feeding power to the light-emitting elements is formed so as to be exposed.
In such a light-emitting device, more heat is generated as output of the light-emitting diodes becomes higher, and the temperature increases as more heat is generated. This results in a decrease in brightness of the light-emitting diodes.
As a conventional art described in an official gazette, there is a container of a light-emitting device composed of a first resin portion and a second resin portion. Here, the first resin portion is formed of a first resin on a side of a lead frame where light-emitting diodes are mounted, and the second resin portion is formed of a second resin on a surface of the lead frame where the light-emitting diodes are not mounted, the second resin having a coefficient of thermal conductivity higher than the first resin (see Patent Document 1).    Patent Document 1: Japanese Patent Application Laid-Open Publication No. 2008-108836